It seems that the satellites reactor coolant system either ruptured due to wear and tear, or the satellite was hit by debris, possibly from the infamous Chinese ASAT test....in any event the satellite has excreted a cloud of stuff....most likely hardened coolant (it used a liquid metal coolant) forming a cloud of metallic pebbles of various sizes on various courses.

This satellite is causing some people concern because is a later version of the well known Cosmos 954 that rained radioactive scrap over several hundred miles of Canadian taiga back in 1978. However, the radioactive threat is limited. Actually it is negligible given that the vehicle is not in a decaying orbit.

What is worrisome is the fact that Cosmos 1818 is still up there and is in lots of little hard to track pieces on different vectors. This greatly adds to the navigational hazards of an orbital torus already very full of dangerous debris, and it can only add to the overall threat of collisions from orbital fragments.

If this was due to a debris strike then it is a mini example of the sort of thing that could easily lead to something called the Kessler Syndrome. That is debris hit satellites and other structures..thereby causing more debris...which in turn cause yet more collisions....this leads to a geometric increase in the generation of hyper-velocity projectiles orbiting in random directions until it is simply impractical due to the high likelihood of catastrophic collisions to continue in space. This sort of thing needs more attention...As it is, we are reinforcing the walls to our own prison.